Pattern steamflooding with horizontal wells

Abstract

Processes and systems comprising a five-spot pattern of multiple horizontal wells for increasing the efficiency of heated vapor-assisted hydrocarbon recovery from subterranean viscous hydrocarbon formations.

1 . A process for recovering viscous hydrocarbons from an underground hydrocarbon formation, comprising the following steps:
 a) drilling a “production unit” comprising three separate and adjacent wellbores into an underground formation containing viscous hydrocarbons;   b) extending each of the three wellbores through said formation in a substantially horizontal direction for a distance greater than thirty meters; said horizontal portion of each wellbore being substantially parallel to the other two wellbores in both horizontal and vertical planes;   c) inserting a tubular liner into each well comprising periodic sections of liner containing one or more orifices, separated by multiple sections of liner without orifices;   d) inserting tubing with a closed end into each wellbore inside of the liner, wherein the tubing contains periodic orifices, and wherein the annular space between the outer wall of the tubing and the inner wall of the liner on either side of each periodic tubular orifice is isolated from the remainder of the wellbore by a device that restricts flow through the annular space;   e) injecting heated vapor into the tubing present in the first and third wellbores, such that the vapor enters the formation and reduces the viscosity of the viscous hydrocarbons contained therein;   f) collecting hydrocarbons exiting the formation via periodic orifices in the tubular liner present in the second wellbore, wherein the second wellbore utilized for hydrocarbon production is centrally located between injection wellbores one and three when viewed from above, and wherein the second wellbore is approximately equidistant to the two adjacent injection wellbores.   
     
     
         2 . The process of  claim 1 , wherein the periodic orifices in the tubular liners of the three adjacent wellbores comprising a production unit are positioned relative to each other such that when viewed from above, a five-spot pattern is formed, with each collection orifice in the tubular liner of wellbore two being encircled by four substantially equidistant steam injection orifices consisting of two orifices in the tubular liner of wellbore one and two orifices in the tubular liner of wellbore three. 
     
     
         3 . The process of  claim 2 , wherein the three adjacent wellbores comprising a production unit are located in a substantially horizontal plane. 
     
     
         4 . The process of  claim 2 , wherein the third well of a first production unit serves as the first well of a second, adjacent production unit. 
     
     
         5 . The process of  claim 4 , wherein multiple, adjacent production units are drilled to cover the width of an entire formation containing viscous hydrocarbons. 
     
     
         6 . The process of  claim 2 , wherein the multiple periodic liner orifices utilized for either injection of heated vapor or for the production of hydrocarbons comprise a member of the group consisting of mesh screens, wire-wrap screens, perforations or slots. 
     
     
         7 . The process of  claim 2 , wherein prior to production from wellbore two, heated vapor is first injected simultaneously into all wellbores until the viscous hydrocarbons present in the underground formation reach a temperature where recovery of the hydrocarbons as a liquid is possible. 
     
     
         8 . The process of  claim 2 , where the distance between injection points in the five-spot pattern is between 10 and 500 meters. 
     
     
         9 . The process of  claim 2 , where the distance between injection points in the five-spot pattern is between 25 and 300 meters. 
     
     
         10 . A system for injecting heated vapor into a formation containing viscous hydrocarbons, and recovering hydrocarbons from the same formation, comprising:
 a) a “production unit” of three separate and adjacent wellbores drilled into an underground formation containing viscous hydrocarbons;
 i. wherein each of the three wellbores is drilled through said formation in a substantially horizontal direction for a distance greater than 30 meters; said horizontal portion of each wellbore drilled substantially parallel to the other two wellbores in both horizontal and vertical planes; 
 ii. and wherein the substantially horizontal section of each wellbore is uncased; 
 iii. and wherein the second wellbore is utilized for hydrocarbon production and centrally located between the first and third wellbores when viewed from above; 
 iv. and wherein the first and third wellbores are utilized for injection of steam into the formation; 
   b) tubing with a closed end inserted into each wellbore, wherein said tubing contains periodic orifices, said orifices being selected from the group consisting of slots, perforations, or wire-wrap screens, or wire mesh screens;   c) a device that regulates the flow of heated vapor through the annulus formed between the injection tubing and the liner wall on either side of each periodic injection orifice;   d) a device for regulating the flow of hydrocarbons through the annulus formed between the production tubing and the liner wall on either side of each periodic production orifice.   
     
     
         11 . The system of  claim 10 , wherein said device for regulating the flow of hydrocarbons comprises a device selected from the group consisting of mechanically-set packers, hydraulically-set packers, inflatable packers or seals. 
     
     
         12 . The system of  claim 10 , wherein the periodic orifices of the three adjacent wellbores comprising a production unit are positioned relative to each other such that when viewed from above, a five-spot pattern is formed, with each collection orifice in the liner of wellbore two being encircled by four substantially equidistant steam injection orifices consisting of two orifices in the liner of wellbore one and two orifices in the liner of wellbore three. 
     
     
         13 . The system of  claim 12 , wherein the three adjacent wellbores comprising a production unit are located in a substantially horizontal plane. 
     
     
         14 . The system of  claim 12 , wherein the third well of a first production unit serves as the first well of a second, adjacent production unit. 
     
     
         15 . The system of  claim 14 , wherein multiple, adjacent production units are drilled to cover the width of an entire formation containing viscous hydrocarbons. 
     
     
         16 . The system of  claim 12 , wherein the multiple periodic liner orifices in each well utilized for either the injection of heated vapor or the production of viscous hydrocarbons comprise mesh screens, wire-wrap screens, perforations, or slots. 
     
     
         17 . The system of  claim 12 , wherein prior to production from wellbore two, heated vapor is first injected simultaneously into all wellbores until the viscous hydrocarbons present in the underground formation reach a temperature where recovery of the hydrocarbons as a liquid is possible. 
     
     
         18 . The system of  claim 12 , where the distance between injection points in the five-spot pattern is between 10 and 500 meters. 
     
     
         19 . The system of  claim 12 , where the distance between injection points in the five-spot pattern is between 25 and 300 meters.